The present invention relates to application of foil to paper, and particularly to conversion of a cylinder press for use in hot die stamping application of foil.
It is well known to apply a coat of material known as a "foil" by a hot die stamping process. Such foil material is provided as a layer of coating material carried, for example, on a supporting web of thin film plastic material. The "foil" coating is released by raising the temperature high enough to release an adhesive bond between the foil and the supporting web, while pressure is applied to cause the foil to adhere to the paper stock in a desired location and pattern.
U.S. Pat. No. 3,296,958 describes a heated plate for use in hot die stamping of foil onto paper and similar stock, and U.S. Pat. No. 3,316,835 describes apparatus for use in conjunction with a printing press of the platen type for carrying out the application of such foil. There are, however, several problems associated with use of cylinder press which are not solved by the platen press conversion apparatus described in U.S. Pat. No. 3,316,835.
A cylinder press includes a cylinder which rotates, carrying a sheet of paper stock on which an impression is to be made. A chase of such a press moves reciprocatingly in mechanical synchronization with rotation of the cylinder, to carry the type, in normal printing, or in the case of hot die foil stamping, to carry a heated die beneath the cylinder, so as to move the type or die at the same speed at which the paper is carried by the cylinder. Foil which is to be applied by such a cylinder press must be held in a position between the die and the paper stock, yet must not touch the heated die except when it is intended to make an impression of foil upon a piece of stock. The heat of the die would otherwise prematurely release contacted portions of the foil from the supporting web. It is thus necessary to support the foil-carrying web so that it is ordinarily kept from touching the hot die.
Because of the high cost of the foils which are used in this process, it is desirable to use the foil with as little waste as possible. It is thus desired to move a long and relatively narrow web of roll-foil material only the minimum distance necessary, after an impression is made on a sheet of stock, to assure that fresh foil is in position for application to the next sheet of stock. Where foil impressions are made in more than one location upon each sheet of stock, the foil-supporting web need be moved only a short distance to provide clear foil for each impression for a certain number of sheets of stock, after which it may be necessary to move the foil supply a larger distance in order to have foil again available for all of the separate impressions to be made upon a subsequent piece of stock.
The present invention supplies apparatus for supporting and moving webs of roll-foil material for hot die stamping using a cylinder press. A supply of foil-carrying web material is wound on a spool carried on an end of the chase of a cylinder press. The web of foil-carrying material extends material extends across the top of the chase above a heated die carried on the chase. The foil-carrying material is supported safely spaced above the surface of the hot die except during the time when it is intended to make a foil impression of the die upon a piece of stock.
A foil draw controller controls operation of a draw roller and a pinch roller which cooperatively move the web of foil-carrying material as needed to provide fresh foil for each subsequent impression. The foil draw controller is adjustable to control the distance the web of foil-carrying material is usually drawn after each impression, to count the number of times the foil is drawn this distance, and to control the draw roller drive thereafter to draw the foil a greater distance to provide fresh foil for a subsequent set of impressions.
The draw roller drive includes a motor and a relay-controlled clutch responsive to the draw controller. A rewind spooling mechanism is also provided to accumulate the remaining portions of the foil material.
An articulated foil support frame, or rack, connects the reciprocatingly moving chase with a fixed frame which supports the draw roller and pinch roller at one end of the cylinder press. The web of foil-carrying material extends around rollers on the articulated support frame so that the web of foil-carrying material is prevented from becoming slack between the supply spool and the draw roller, despite the motion of the chase.
It is therefore a principal object of the present invention to provide a conversion mechanism which can be attached to a cylinder press quickly and easily to enable such cylinder press to be used for foil stamping operations while utilizing, as far as possible, the operative mechanism of the cylinder press, so as to avoid the need for a special press for hot die stamping.
It is another object to utilize the automatic paper-handling mechanism of the cylinder press in the stamping operation and to provide a stamping press operation having operating characteristics as automatic as those of the cylinder press.
It is a further object of the present invention to provide apparatus for controlling the rate at which the web of foil-carrying material is moved across the chase, in accordance with the size of the stamping die so as to provide a fresh foil surface for each stamping operation, while conserving the foil-carrying material as much as possible.
It is an important feature of the present invention that the foil drawing mechanism and the foil draw control system are adjustable to pull an adjustable multiple of short draws, followed by a long draw, of foil from a supply roll of foil-carrying material, and to continue such a sequence during a foil-stamping run of many sheets of stock.
It is an important advantage of the present invention that it provides for increased economy of foil utilization.
It is another advantage of the present invention that it makes it unnecessary to provide a separate press for hot die foil stamping use.
The foregoing and other objectives, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.